Syrian Hamster as a Permissive Model for Testing Anti-Adenovirus Drugs

描述（由申请人提供）：人腺病毒（Ad）是免疫抑制人群中的一个重要问题，特别是在接受同种异体干细胞移植的儿童中。这些儿科患者中约20%发展为播散性Ad感染，约一半的患者死亡。没有抗病毒药物被批准用于治疗这些Ad感染。在某些情况下使用西多福韦和利巴韦林，但不知道它们是否有效，因为它们没有以系统的对照方式进行研究。抗Ad药物的开发受到阻碍，因为没有复制人类Ad的动物模型。这是因为广告具有高度的物种特异性。我们正在开发叙利亚仓鼠作为肿瘤模型，以研究溶瘤Ad载体的功效、复制、毒性和生物分布。我们发现，人Ad血清型5（Ad 5）和Ad 5为基础的溶瘤载体复制以及仓鼠肿瘤，肝，肺，和其他器官的肿瘤内或静脉注射后。非常有趣的是，使用环磷酰胺（CP）对仓鼠进行免疫抑制导致病毒复制水平更高。病毒给药后，复制在肿瘤和肝脏中以高水平持续至少42天（实验结束）。基于这些观察结果，我们建议使用CP免疫抑制的叙利亚仓鼠作为一种新的动物模型，以评估疗效和毒理学的抗Ad药物对播散性Ad感染的免疫功能低下的患者。为了获得该模型的初步原理验证，我们将评估十六烷氧基丙基西多福韦（HDP-CDV）的抗Ad功效和毒理学。在具体目标1中，我们将检查HDP- CDV对CP免疫抑制的仓鼠肝脏中Ad 5（人Ad物种C的成员）复制的抑制。将通过qPCR、组织培养感染剂量测定50（TCID 50测定）和Ad病毒体蛋白的免疫组织化学测定肝脏和血液中的Ad 5复制。将根据肝脏组织病理学和血清化学评估毒性。在目的2中，我们将确定人Ad种类A、B、D、E和F中的血清型是否在CP免疫抑制的仓鼠的肝脏中复制。如果它们确实复制，那么我们将确定HDP-CDV是否抑制它们在培养细胞中的复制。 当人类变得严重免疫抑制时，例如当白血病儿童在接受骨髓干细胞移植之前免疫抑制药物破坏其免疫系统时，这些患者通常会发生不同病毒的全身感染。这些感染可能是由于新的感染或潜伏病毒的激活，因为患者的免疫系统无法控制病毒而发生。腺病毒是引起这些感染的病毒类型之一，并且感染经常导致患者死亡。不幸的是，在对照临床试验中没有检查过抗腺病毒药物，因此没有药物被批准用于治疗这些腺病毒感染。尚未进行抗腺病毒药物的临床试验的一个原因是因为没有合适的动物模型可用于测试此类药物的有效性和毒性。在这项资助申请中，我们建议开发叙利亚仓鼠作为免疫抑制动物模型，以评估抗腺病毒药物。该项目的成功可能导致最终批准用于治疗免疫抑制患者腺病毒感染的药物。

DESCRIPTION (provided by applicant): Human adenoviruses (Ads) are a significant problem in immunosuppressed humans, especially in children undergoing allogeneic stem cell transplants. About 20% of these pediatric patients develop disseminated Ad infections and about half of the patients die. There are no anti-viral drugs approved to treat these Ad infections. Cidofovir and ribavirin are used in some cases, but it is not known whether they are effective because they have not been studied in a systematic controlled manner. Development of anti-Ad drugs has been hindered because there is no animal model for replicating human Ads. This is because Ads are highly species-specific. We are developing the Syrian hamster as a tumor model to study the efficacy, replication, toxicity, and biodistribution of oncolytic Ad vectors. We showed that human Ad serotype 5 (Ad5) and Ad5-based oncolytic vectors replicate well in hamster tumors, livers, lungs, and other organs following intratumoral or intravenous injection. Of great interest, immunosuppression of the hamsters using cyclophosphamide (CP) leads to much higher levels of replication of the viruses. Replication continues at high levels in tumors and livers for at least 42 days (the end of the experiment) following administration of the virus. Based on these observations, we propose to use CP-immunosuppressed Syrian hamsters as a new animal model to evaluate the efficacy and toxicology of anti-Ad drugs on disseminated Ad infections in immunocompromised patients. To obtain initial proof-of-principle for this model, we will evaluate the anti-Ad efficacy and toxicology of hexadecyloxypropyl-cidofovir (HDP-CDV). In Specific Aim 1 we will examine HDP- CDV inhibition of Ad5 (a member of human Ad Species C) replication in the liver of hamsters immunosuppressed by CP. Ad5 replication in the liver and blood will be determined by qPCR, a tissue culture infectious dose assay 50 (TCID50 assay), and immunohistochemistry for an Ad virion protein. Toxicity will be assessed based on histopathology of the liver and serum chemistry. In Aim 2 we will determine whether serotypes in human Ad Species A, B, D, E, and F replicate in the liver of hamsters immunosuppressed by CP. If they do replicate, then we will determine whether HDP-CDV inhibits their replication in cultured cells. When humans become severely immunosuppressed, for example when children with leukemia have their immune system destroyed by immunosuppressed drugs prior to receiving bone marrow stem cell transplants, these patients often develop systemic infections with different viruses. These infections, which may be due to new infections or to activation of latent viruses, occur because the patient's immune system cannot keep the virus in check. Adenoviruses are one of the types of viruses that cause these infections, and the infections frequently result in the death of the patient. Unfortunately, no anti-adenovirus drugs have been examined in controlled clinical trials, and therefore no drugs are approved to treat these adenovirus infections. One reason that clinical trials for anti-adenovirus drugs have not been conducted is because there is no suitable animal model available to test the effectiveness and toxicity of such drugs. In this grant application, we propose to develop the Syrian hamster as an immunosuppressed animal model to evaluate anti-adenovirus drugs. Success in this project could lead to the eventual approval of drugs to treat adenovirus infections in immunosuppressed patients.